Generally, remote sensors located within an environment transmit information and measurements of sensing occurrences in the environment to a main control unit. In residential, commercial, and industrial environments the remote sensors are static i.e. the remote sensors are fixed at a location in which it can best detect occurrences like temperature, humidity, environmental gases, carbon monoxide, carbon dioxide, motion, glass break, door open, or security alarm, fire, occupancy, light, ultraviolet light, passive infrared, motion, water level, oxygen, volatile organic compounds, air flow, water flow, pressure, or sound, but not limited to these occurrences. Remote sensors detect these occurrences and transmit the information over wired or wireless interfaces.
Wireless remote sensors are generally powered by a power line or battery. Wireless remote sensors generally operate part of the time in a sleep or inactive state partly detecting occurrences which it is intended to sense. The common activities involved in sensing may be wakeup, sense, process, and transmit and receive information via radio-frequency transmission. The battery power consumption of the remote wireless sensor are generally dependent on the transmit and receive activities, the duration of the message and the radio frequency (RF) transmission power level of the radio-frequency energy to be transmitted. The radio-frequency transmit field strength is normally represented in decibel-milliwatts. In the case of a wireless remote sensor running on a battery, the transmit time and RF transmission power level has an impact on the lifespan of the battery. Typically, the RF transmission power is directly proportional to the range in which the wireless remote sensor can transmit information.
The wireless remote sensor is typically factory programmed to a maximum RF transmission power level to achieve a maximum range, or is factory programmed to a RF transmission power level which will achieve a stipulated range of the sensor. For example, to achieve a maximum range of 100 meters, a wireless remote sensor may be required to transmit the message over its radio-frequency at 5 decibel-milliwatts. The remote sensor will be factory programmed to transmit at 5 decibel-milliwatt RF transmission power level. Accordingly, all wireless remote sensors, regardless of their level of proximity to a main control unit, consume the same amount of battery power to communicate with the main control unit.
In most environments, the main control unit is the one which controls the end equipment based the on the data received from the sensors. The wireless remote sensors are arranged one or more in a zone. There may be multiple zones in the environment. For the wireless remote sensors which operate on batteries, the RF transmission power of the wireless remote sensor has an impact on the life of the battery. Typically, the transmit power of the wireless sensor is already programmed to max value. While the sensors located at the edge of the range have to transmit messages at the max value of the RF transmission power, even sensors located close to the main control unit will transmit at this max value of RF transmission power level as they are factory programmed to do so. If a sensor is out of range, a repeater, range extender, aggregator or protocol conversion device is used to communicate the data sent by the wireless sensor. Additionally, obstructions in the environment may create path loses of some sensors. Because all of the sensors are factory pre-programmed to operate at a predetermined RF transmission power level, some sensors may waste battery power, thereby draining the battery of the sensor.
A need remains for a system that controls the RF transmission power level of a wireless remote sensor at an optimum RF transmission power level that saves battery power.